Filter assembly

ABSTRACT

There is provided a filter assembly arranged to be mounted over the air inlet of a fan assembly, the filter assembly comprising a filter frame arranged to support one or more filter media. The filter frame is provided with a first engagement member on a first edge of the filter frame and a second engagement member on a second edge of the filter frame, the first edge being opposite to the second edge. The first engagement member and the second engagement member are each configured to be engaged by a respective retention assembly when mounted on the fan assembly.

REFERENCE TO RELATED APPLICATIONS

This application claims the priority of United Kingdom Application No.1720057.7, filed Dec. 1, 2017, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to filter assembly arranged to be mountedover the air inlet of a fan assembly.

BACKGROUND OF THE INVENTION

A conventional domestic fan typically includes a set of blades or vanesmounted for rotation about an axis, and drive apparatus for rotating theset of blades to generate an airflow. The movement and circulation ofthe airflow creates a ‘wind chill’ or breeze and, as a result, the userexperiences a cooling effect as heat is dissipated through convectionand evaporation. The blades are generally located within a cage whichallows an airflow to pass through the housing while preventing usersfrom coming into contact with the rotating blades during use of the fan.

U.S. Pat. No. 2,488,467 describes a fan which does not use caged bladesto project air from the fan assembly. Instead, the fan assemblycomprises a base which houses a motor-driven impeller for drawing anairflow into the base, and a series of concentric, annular nozzlesconnected to the base and each comprising an annular outlet located atthe front of the nozzle for emitting the airflow from the fan. Eachnozzle extends about a bore axis to define a bore about which the nozzleextends.

Each nozzle is in the shape of an airfoil may therefore be considered tohave a leading edge located at the rear of the nozzle, a trailing edgelocated at the front of the nozzle, and a chord line extending betweenthe leading and trailing edges. In U.S. Pat. No. 2,488,467 the chordline of each nozzle is parallel to the bore axis of the nozzles. The airoutlet is located on the chord line, and is arranged to emit the airflowin a direction extending away from the nozzle and along the chord line.

Another fan assembly which does not use caged blades to project air fromthe fan assembly is described in WO 2010/100451. This fan assemblycomprises a cylindrical base which also houses a motor-driven impellerfor drawing a primary airflow into the base, and a single annular nozzleconnected to the base and comprising an annular mouth/outlet throughwhich the primary airflow is emitted from the fan. The nozzle defines anopening through which air in the local environment of the fan assemblyis drawn by the primary airflow emitted from the mouth, amplifying theprimary airflow. The nozzle includes a Coanda surface over which themouth is arranged to direct the primary airflow. The Coanda surfaceextends symmetrically about the central axis of the opening so that theairflow generated by the fan assembly is in the form of an annular jethaving a cylindrical or frusto-conical profile.

WO 2010/046691 also describes a fan assembly. The fan assembly comprisesa cylindrical base which houses a motor-driven impeller for drawing aprimary air flow into the base, and an annular nozzle connected to thebase and comprising an annular air outlet through which the primary airflow is emitted from the fan. The fan assembly comprises a filter forremoving particulates from the air flow. The filter may be providedupstream from motor-driven impeller, in which case particulates areremoved from the air flow prior to passing through the impeller. Thisprotects the impeller from debris and dust that may be drawn into thefan assembly and which may damage the fan assembly. Alternatively, thefilter may be provided downstream from the motor-driven impeller. Inthis configuration it is possible to filter and clean the air drawnthrough the motor-driven impeller, including any exhaust emissions,prior to progression through the elements of the fan assembly and supplyto the user.

WO2016/128732 describes a fan assembly similar to those of WO2010/100451 and WO 2010/046691. The fan assembly is provided with airinlets that extend around the entire circumference of the body of thefan in order to maximise the area available for air to be drawn into thefan assembly. The fan assembly is therefore also provided with atubular, barrel-type filter that fits concentrically over the body ofthe fan and surrounds the entire circumference of the fan body upstreamfrom the air inlets, and a nozzle that is removably mounted on the body.The filter is not connected to either the body or the nozzle but issecurely held in place by the nozzle when mounted on the body, and canonly be removed from the fan assembly after removal of the nozzle. Thisarrangement provides that the filter may simply be lowered onto the bodybefore being secured in place by the engagement of the nozzle with thebody and further provides that the filter can easily be removed from thebody after removal of the nozzle in order to allow for cleaning orreplacement of the filter.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a filter assemblyarranged to be mounted over the air inlet of a fan assembly that can beremoved (e.g. for cleaning and/or replacement) without the need toremove the nozzle from the fan body, whilst still optimising the areaavailable for air to be drawn into the fan assembly.

To do so, the present invention provides a filter assembly arranged tobe mounted over the air inlet of a fan assembly that comprises a pair ofengagement members that are provided on opposing edges of the fanassembly and that are each arranged to be engaged by a respectiveretention assembly when mounted on the fan assembly. Providing thefilter assembly with a pair of engagement members allows the filterassembly to be mounted and retained on the body of a fan assembly by thesimply sliding the filter assembly sideways onto the fan body so thatthe engagement members are each engaged by a corresponding retentionassembly. The filter assembly can then also be removed from the fan bodysimply by releasing the engagement members from the retention assembliesand lifting them sideways away from the fan body without the need toremove the nozzle.

By doing away with the need to remove the nozzle in order to remove thefilters from the fan assembly, the present invention provides that thenozzle and/or the neck of the nozzle of the fan assembly can incorporatecomponents and/or functionality that could not easily be incorporatedinto a removable nozzle.

In a first aspect, the present invention provides a filter assemblyarranged to be mounted over the air inlet of a fan assembly, the filterassembly comprising a filter frame arranged to support one or morefilter media. The filter frame is provided with a first engagementmember on a first edge of the filter frame and a second engagementmember on a second edge of the filter frame, the first edge beingopposite to the second edge. The first engagement member and the secondengagement member are each configured to be engaged by a respectiveretention assembly when mounted on the fan assembly. Preferably, thefilter frame has two-fold rotational symmetry such that the filter framecan be retained on the fan assembly in either of two opposingorientations.

Preferably, the first engagement member provided on the first edge ofthe filter frame is located towards a first end of the filter frame, andthe second engagement member provided on the second edge of the filterframe is located towards an opposing, second end of the filter frame. Adistance between the first engagement member and the first end of thefilter frame may then be equal to a distance between the secondengagement member and the second end of the filter frame. The firstengagement member may be adjacent to a first corner of the filter frameand the second engagement member may be adjacent to a diagonallyopposing second corner of the filter frame.

Preferably, the first engagement member and the second engagement membereach comprise a pair of hooks that face in opposing directions. Eachhook may comprise a projection extending from the filter frame having adistal end that is angled relative to a proximal end, the distal endextending in a direction that is parallel to the longitudinal axis ofthe filter frame. Each pair of hooks may comprise a single projectionextending from the filter frame having a distal end comprising a pair ofangled portions that are parallel to the longitudinal axis of the filterframe and that extend in opposing directions.

Preferably, the filter frame is provided with a first side flange thatextends along a first side of the filter frame and a second side flangethat extends along a second side of the filter frame. More preferably,the first side flange extends along the entirety of the first side ofthe filter frame and the second side flange that extends along theentirety of the second side of the filter frame. These side flangesprovide surfaces to which the filter media can be sealed using glue onthe downstream side of filter assembly and also provide surfaces thatallow the filter frame to form a seal with the body of the fan (e.g.with corresponding flanges on the body) to prevent air from leaking intoor out of the fan body without passing through the filter media. Thefirst engagement member may then be provided on the first side flangeand the second engagement member provided on the second side flange.

The filter frame may be provided with a first end flange that extendsalong a first end of the filter frame and a second side flange thatextends along a second end of the filter frame, the first end flange andthe second end flange being arranged to support the one or more filtermedia. More preferably, the first end flange extends around the entiretyof the first end of the filter frame and the second side flange thatextends around the entirety of the second end of the filter frame. Theseend flanges also provide surfaces to which the filter media can besealed using glue on the downstream side of filter assembly, providesurfaces that allow the filter frame to form a seal with the body of thefan (e.g. with corresponding flanges on the body) to prevent air fromleaking into or out of the fan body without passing through the filtermedia, and also provide support for the filter media provided on thefilter frame.

Preferably, the filter frame is provided with a seal that extends aroundthe entirety of an inner/inwardly facing periphery of the filter frame.The filter frame may be provided with a recess that that extends aroundthe entirety of the inner periphery of the filter frame and that isarranged to received and support the seal. The recess may extend acrossan inner surface of both the first side flange and second side flange,and across an inner edge of both the first end and the second end of thefilter frame.

Preferably, the filter assembly further comprises a first retentionmember provided on a first end of the filter frame and a secondretention member provided on an opposing, second end of the filterframe, wherein the first retention member and the second rotation memberare arranged to releasably retain a shroud when mounted on the filterassembly. More preferably, the first retention member is provided on thefirst end flange of the filter frame, and the second retention member isprovided on the second end flange of the filter frame.

Each of the first retention member and the second retention member maycomprise a resilient catch or hook that is arranged to engage acorresponding through-hole provided on the shroud. The resilient catchor hook comprises a resilient arm or tab, a distal end of the resilienttab being provided with a sloped projection, wherein the slopedprojection slopes downwards towards the distal end of the resilient tab.Preferably, the resilient arm or tab extends in a direction that isparallel to a plane that bisects the filter frame and the slopedprojection projects/extends away from the exterior/external surface ofan end flange of the filter frame.

Preferably, the filter frame is provided with one or more alignment ribsthat are arranged to cooperate with a corresponding track or channel orgroove provided on the shroud in order to guide the shroud onto thefilter frame (i.e. so that each of the shroud retention members engage arespective shroud retention though-hole). Preferably, the or eachalignment rib is straight and extends in a direction that is parallel toa longitudinal plane that bisects the filter frame. The or eachalignment rib is therefore perpendicular to the longitudinal axis of thefilter frame.

The filter frame may be provided with at least one alignment rib on eachend of the filter frame. The first end flange and the second end flangeof the filter frame may then each be provided with a pair of alignmentribs. The alignment ribs then project/extend away from and extend alongthe exterior/external surface of the flange. Preferably, a first of thepair of alignment ribs is provided towards a first end of the flange anda second of the pair of alignment ribs is provided towards an opposite,second end of the flange.

Preferably, the first end flange and the second end flange of the filterframe are each provided with a further pair of alignment ribs. Each ofthe second pair of alignment ribs may be provided on opposite sides ofthe engagement member provided on the end flange.

Preferably, the filter assembly is substantially semi-cylindrical inshape. The filter assembly may then have the shape of a partial tubethat is configured to cover a portion of the periphery/outer surface ofthe generally cylindrical fan body. The edges of the filter frame maytherefore be parallel to the longitudinal axis of the filter frame, withthe ends of the filter frame being perpendicular to a longitudinal axisof the of the filter frame and having an arc-shaped cross section in aplane perpendicular to longitudinal axis.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1a is a front view of an embodiment of a fan assembly;

FIG. 1b is a right side view of the fan assembly of FIG. 1 a;

FIG. 2 is a right side cross-section view, taken along line A-A in FIG.1 a;

FIG. 3 is an enlarged view of a portion of the cross-section view ofFIG. 2;

FIG. 4 is a perspective view of a main body section of the fan assemblyof FIGS. 1a and 1 b;

FIG. 5a is an exploded view of the filter assembly of the fan assemblyof FIGS. 1a and 1 b;

FIG. 5b is a rear perspective view of the filter assembly of FIG. 5 a;

FIG. 6 is a rear perspective view of a perforated shroud of the fanassembly of FIGS. 1a and 1 b;

FIG. 7a is a front exploded view of a retention assembly of the fanassembly of FIGS. 1a and 1 b;

FIG. 7b is a rear exploded view of the retention assembly of FIG. 7 a;

FIG. 7c is a rear view of the retention assembly of FIG. 7a and enlargedviews of the bistable catches of the retention assembly; and

FIG. 8 is a cutaway view of one of the retention assemblies.

DETAILED DESCRIPTION OF THE INVENTION

There will now be described a purifying fan assembly comprising one ormore filter assemblies and mechanisms for retaining and releasing thefilter assemblies that provide several advantages over those ofconventional fan assemblies. The term “fan assembly” as used hereinrefers to a fan assembly configured to generate and deliver an airflowfor the purposes of thermal comfort and/or environmental or climatecontrol. Such a fan assembly may be capable of generating one or more ofa dehumidified airflow, a humidified airflow, a purified airflow, afiltered airflow, a cooled airflow, and a heated airflow.

The fan assembly comprises a body or stand, a motor-driven impellercontained within the fan body and arranged to generate an airflow, and anozzle mounted on and supported by the fan body, the nozzle beingarranged to receive the airflow from the fan body and to emit theairflow from the fan assembly. The fan body is provided with a pair ofair inlets through which air enters the body (i.e. through which air isdrawn into the fan body by the motor-driven impeller). Specifically, thefan body is provided with a first air inlet and a second air inlet, thefirst air inlet and the second air inlet being on opposing halves of thefan body.

The fan assembly then further comprises two separate filter assembliesthat each comprise a filter frame supporting one or more filter mediaand that are each arranged to be mounted on the fan body over arespective one of the air inlets. The filter assemblies are thereforelocated upstream relative to the air inlets of the fan body. Preferably,the two filter frames are identical and are therefore interchangeable.

The fan assembly is then provided with a pair of retention assembliesthat cooperate to releasably retain the two filter assemblies on the fanbody. To do so, the fan body comprises a first retention assembly thatis configured to releasably engage both a first filter frame adjacent toa first edge of the first filter frame and a second filter frameadjacent to a first edge of the second filter frame, and a secondretention assembly that is configured to releasably engage both thefirst filter frame adjacent to a second edge of the first filter frameand the second filter frame adjacent to a second edge of the secondfilter frame. The first edge of the first filter frame is opposite tothe second edge of the first filter frame, and the first edge of thesecond filter frame is opposite to the second edge of the second filterframe.

FIGS. 1a and 1b are external views of an embodiment of a free-standingenvironmental control fan assembly 1000, and FIG. 2 show a sectionalview through lines A-A of FIG. 1a . FIG. 3 then shows an enlargedsectional view of the body 1100 of the fan assembly 1000 illustrated inFIGS. 1a and 1 b.

As shown in FIGS. 2 and 3, the body 1100 comprises a substantiallycylindrical main body section 1110 mounted on a substantiallycylindrical lower body section 1120. The main body section 1110 has asmaller external diameter than the lower body section 1120. The mainbody section 1110 has a lower annular flange 1111 that extendsradially/perpendicularly away from the lower end of the main bodysection 1110. The outer edge of the lower annular flange 1111 issubstantially flush with the external surface of the lower body section1120. The removable filter assemblies 1300 are then mounted on the mainbody section 1110, resting on the lower annular flange 1111 of the mainbody section 1110. In this embodiment, the main body section 1110further comprises an upper annular flange 1112 that extendsradially/perpendicularly away from an opposite, upper end of the mainbody section 1110. The outer edge of the upper annular flange 1112 isthen substantially flush with the external surface of a base/neck 1250of the nozzle 1200 that connects to upper end of the main body section1110.

As shown in FIGS. 3 and 4, the main body section 1110 comprises aperforated cylindrical housing 1119 that contains various components ofthe fan assembly 1000. The perforated housing 1119 comprises twoseparate arrays of apertures which act as the air inlets 1130 a, 1130 bof the body 1100 of the fan assembly 1000. A first air inlet 1130 a ofthe fan assembly 1000 is provided by a first array of apertures providedon a first half/portion of the circular cylindrical housing 1119 thatextends over the entire length/height of the main body section 1110, anda second inlet 1130 b of the fan assembly 1000 is provided by a secondarray of apertures provided on a second half/portion of the circularcylindrical housing 1119 that extends over the entire length/height ofthe main body section 1110. Alternatively, each of the air inlets 1130a, 1130 b could comprise one or more grilles or meshes mounted withinwindows formed in the main body section 1110.

A filter assembly 1300 is then located upstream from each of the airinlets 1130 a, 1130 b of the main body section 1110, such that the airdrawn into the main body section 1110 by the impeller 1150 is filteredprior to entering the main body section 1110. This serves to remove anyparticles which could potentially cause damage to the fan assembly 1000,and also ensures that the air emitted from the nozzle 1200 is free fromparticulates. In addition, this also serves to remove various chemicalsubstances from that could potentially be a health hazard so that theair emitted from the nozzle 1200 is purified. The main body section 1110is open at the upper end thereof to accommodate the air vent/opening1115 through which the primary airflow is exhausted from the body 1100.

The lower body section 1120 comprises a further housing containingcomponents of the fan assembly 1000 other than those contained withinmain body section 1110. The lower body section 1120 is mounted on a base1140 for engaging a surface on which the fan assembly 1000 is located.Specifically, the base 1140 supports the fan assembly 1000 when locatedon a surface with the nozzle 1200 uppermost relative to the base 1140.In this embodiment, the lower body section 1120 houses a pan drive gear(not shown) that is engaged by a pan pinion (not shown). The pan pinionis driven by an oscillation motor 1160 housed within the bottom of themain body section 1110. Rotation of the pan pinion by the oscillationmotor 1160 therefore causes the main body section 1110 to rotaterelative to the lower body section 1120. A mains power cable (not shown)for supplying electrical power to the fan assembly 1000 extends throughan aperture 1121 formed in the lower body section 1120. The external endof the cable is then connected to a plug for connection to a mains powersupply.

The main body section 1110 houses the impeller 1150 for drawing theprimary airflow through the air inlets 1130 a, 1130 b and into the body1100. Preferably, the impeller 1150 is in the form of a mixed flowimpeller. The impeller 1150 is connected to a rotary shaft 1151extending outwardly from a motor 1152. In the embodiment illustrated inFIGS. 2 and 3, the motor 1152 is a DC brushless motor having a speedwhich is variable by a main control circuit 1170 in response to controlinputs provided by a user. The motor 1152 is housed within a motorbucket 1153 that comprises an upper portion 1153 a connected to a lowerportion 1153 b. The upper portion 1153 a of the motor bucket furthercomprises a diffuser 1153 c in the form of an annular disc having curvedblades.

The motor bucket 1153 is located within, and mounted on, an impellerhousing 1154 that is mounted within the main body section 1110. Theimpeller housing 1154 comprises a generally frusto-conical impeller wall1154 a and an impeller shroud 1154 b located within the impeller wall1154 a. The impeller 1150, impeller wall 1154 a and an impeller shroud1154 b are shaped so that the impeller 1150 is in close proximity to,but does not contact, the inner surface of the impeller shroud 1154 b. Asubstantially annular inlet member 1155 is then connected to the bottomof the impeller housing 1154 for guiding the primary airflow into theimpeller housing 1154.

In the embodiment illustrated in FIGS. 2 and 3, the air vent/opening1115 through which the primary airflow is exhausted from the body 1100is defined by the upper portion of the motor bucket 1153 a and theimpeller wall 1154 a. A flexible sealing member 1156 is then attachedbetween the impeller housing 1154 and the main body section 1120. Theflexible sealing member 1156 prevents air from passing around the outersurface of the impeller housing 1154 to the inlet member 1155. Thesealing member 1156 preferably comprises an annular lip seal, preferablyformed from rubber.

The nozzle 1200 is mounted on the upper end of the main body section1110 over the air vent 1115 through which the primary airflow exits thebody 1100. The nozzle 1200 comprises a neck/base 1250 that connects toupper end of the main body section 1110, and has an open lower end whichprovides an air inlet 1240 for receiving the primary airflow from thebody 1100. The external surface of the base 1250 of the nozzle 1200 isthen substantially flush with the outer edge of the upper annular flange1112 of the main body section 1110. The base 1250 therefore comprises ahousing that covers/encloses any components of the fan assembly 1000that are provided on the upper surface 1112 of the main body section1110.

In the embodiment illustrated in FIGS. 2 and 3, the main control circuit1170 is mounted on the upper surface of the upper annular flange 1112that extends radially away from the upper end of the main body section1110. The main control circuit 1170 is therefore housed within base 1250of the nozzle 1200. In addition, an electronic display 1180 is alsomounted on the upper annular flange 1112 of the main body section 1110and therefore housed within base 1250 of the nozzle 1200, with thedisplay 1180 being visible through an opening or at least partiallytransparent window provided in the base 1250. Optionally, one or moreadditional electronic components may be mounted on the upper surface ofthe upper annular flange 1112 and consequentially housed within base1250 of the nozzle 1200. For example, these additional electroniccomponents may one or more wireless communication modules, such asWi-Fi, Bluetooth etc., and one or more sensors, such as an infraredsensor, a dust sensor etc., and any associated electronics. Any suchadditional electronic components would then also be connected to themain control circuit 1170.

The nozzle 1200 comprises an interior passage 1230 for conveying airfrom the air inlet 1240 of the nozzle 1200 to at least one air outlet1210 of the nozzle 1200. The nozzle 1200 therefore comprises one or morecasing sections 1260 that define the interior passage 1230. These casingsections 1260 also define or are provided with at least one slot 1220that forms an air outlet 1210 of the nozzle 1200. The airflow drawnthrough the fan assembly 1000 by the motor-driven impeller 1150 andemitted from the air outlet 1210 of the fan assembly 1000 is referred tohereafter as a primary airflow. The nozzle 1200 also defines acentral/inner opening/bore 1500. The nozzle 1200 therefore forms a loopthat extends around and surrounds the bore 1500. Any portion of theprimary airflow that is emitted from the air outlet 1210 entrains airfrom outside the fan assembly 1000 so that it is drawn through the bore1500, with this entrained air being referred to herein as a secondaryairflow. The primary airflow therefore combines with the entrainedsecondary airflow to form a combined, or amplified, airflow projectedforward from the front of the nozzle. The nozzle 1200 therefore acts asan air amplifier to supply both the primary airflow and the entrainedsecondary airflow to the user.

In the embodiment illustrated in FIGS. 1a, 1b and 2, the nozzle 1200 hasan elongate annular shape, often referred to as a stadium shape, anddefines an elongate opening 1500 having a height greater than its width.The nozzle 1200 therefore comprises two relatively straight sections1201, 1202 each adjacent a respective elongate side of the opening 1500,an upper curved section 1203 joining the upper ends of the straightsections 1201, 1202, and a lower curved section 1204 joining the lowerends of the straight sections 1201, 1202.

As described above, the fan assembly 1000 comprises two separate filterassemblies 1300 a, 1300 b that are each configured to be located on andcover one of the air inlets 1130 a, 1130 b that are provided on theopposing halves of the main body section 1110. Each filter assembly 1300therefore substantially has the shape of a semi-cylinder/tube that cantherefore be located concentrically over the main body section 1110,resting on the lower annular flange 1111 of the main body section 1110.In other words, each filter assembly 1300 has the shape of a partialtube that is configured to cover a portion of the periphery/outersurface of the generally cylindrical main body section 1110.Accordingly, FIG. 4 shows a perspective view of the main body section1110 of the fan assembly 1000, with one of the filter assemblies 1300 bremoved and with the other of the filter assemblies 1300 a mounted onthe far side of the main body section 1110 with a perforated shroud 1400a attached to the outer surface of the filter assembly 1300 a.

FIG. 5a illustrates an exploded view of an embodiment of a filterassembly 1300 suitable for use with the fan assembly of FIGS. 1 to 4. Inthis embodiment, each filter assembly 1300 comprises a filter frame 1310that supports one or more filter media. In the embodiment illustrated inFIG. 5a , each filter frame 1310 substantially has the shape of asemi-cylinder with two straight sides that are parallel to thelongitudinal axis of the filter frame 1310 and two curved ends that areperpendicular to the longitudinal axis of the filter frame 1310. The oneor more filter media are arranged so as to cover the surface areadefined by the filter frame 1310.

The filter frame 1310 is provided with a first end flange 1311 thatextends radially/perpendicularly away from a first curved end of thefilter frame 1310 and a second end flange 1312 that extendsradially/perpendicularly away from an opposite, second curved end of thefilter frame 1310. Each filter frame 1310 is then also provided with afirst side flange 1313 that extends perpendicularly away from a firstside of the filter frame 1310, from a first end of the first end flange1311 to a first end of the second end flange 1312, and a second sideflange 1314 that extends perpendicularly away from a second side of thefilter frame 1310, from a second end of the first end flange 1311 to asecond end of the second end flange 1312. The first end flange 1311,second end flange 1312, first side flange 1313 and second side flange1314 are integrally formed with one another to thereby form a ridge orrim that extends around the entire periphery of the filter frame 1310.The flanges 1311-1314 provide surfaces to which the filter media can besealed (e.g. using glue on the downstream side of filter assembly 1310)and also provide surfaces that allow the filter frame 1310 to form aseal with the main body 1110 of the fan assembly 1000 (e.g. withcorresponding flanges on the main body section 1110) to prevent air fromleaking into or out of the fan body 1100 without passing through thefilter media.

Each filter assembly 1300 further comprises a flexible seal 1330provided around the entirety of an inner periphery of the filter frame1310 for engaging with the main body section 1110 to prevent air frompassing around the edges of the filter assembly 1300 to the air inlet1110 of the main body section 1120, as illustrated in FIG. 5b . Theflexible filter seal 1330 preferably comprises lower and upper curvedseal sections that substantially take the form of an arc-shaped wiper orlip seal, with the each end of the lower seal section being connected toa corresponding end of the upper seal section by two straight sealsections that each substantially take the form of a wiper or lip seal.The upper and lower curved seal sections are therefore arranged tocontact the curved upper and lower ends of the main body section 1110,whilst the straight seal sections are arranged to contact one or otherof two diametrically opposed, longitudinal flanges 1113, 1114 thatextend perpendicularly away from the main body section 1110. Preferably,the filter frame 1310 is provided with a recess (not shown) that extendsaround the entirety of the inner periphery of the filter frame 1310 andthat is arranged to receive and support the seal 1330. In theillustrated embodiment, this recess extends across an inner surface ofboth the first side flange 1313 and second side flange 1314, and acrossan inner edge of both the first end and the second end of the filterframe 1310.

One or more filter media 1321, 1322 are then supported on the outer,convex face of the filter frame 1310, extending across the area betweenthe first and second flanges 1311, 1312 and the first second sideflanges 1313, 1314. In the illustrated embodiment, each filter assembly1300 a, 1300 b comprises a particulate filter media layer 1321 coveredwith an outer mesh layer 1322 attached on the outer face of the filterframe 1310. Optionally, one or more further filter media 1323 can thenbe located within the inner, concave face of the filter frame 1310. Forexample, these further filter media could comprise a first chemicalfilter media layer covered by a second chemical filter media layer thatare both located within the inner face of the filter frame 1210. Thesefurther filter media 1323 could either be attached to and/or support onthe inner, concave face of the filter frame 1310 or alternatively couldbe mounted on to the main body section 1110, resting on the lowerannular flange 1111 of the main body section 1110 beneath each filterassembly 1300 a, 1300 b. In either case, the filter frame 1310 will beformed so that it defines a space within the inner, concave face of thefilter frame 1310 within which these further filter media 1323 can beaccommodated when the filter assembly 1300 is mounted onto the main bodysection 1110.

As illustrated in FIG. 4, a perforated shroud 1400 is then releasablyattached concentrically to the filter frame 1310 so as to cover thefilter assembly 1300 when located on the main body section 1110. FIG. 6shows a perspective view of such a perforated shroud 1400 that issubstantially in the shape of a semi-cylinder. The perforated shroud1400 therefore has two curved ends 1401, 1402 that are perpendicular tothe longitudinal axis of the perforated shroud 1400 and two straightedges 1403, 1404 that are parallel to the longitudinal axis of theperforated shroud 1400. The perforated shrouds 1400 each comprise anarray of apertures which provide an air inlet 1405 through the shroud1400. Alternatively, the air inlet 1405 of the shroud 1400 may compriseone or more grilles or meshes mounted within windows in the shroud 1400.It will also be clear that alternative patterns of air inlet arrays areenvisaged within the scope of the present invention. When mounted onfilter fame, the shrouds 1400 protect the filter media 1321-1324 fromdamage, for example during transit, and also provide a visuallyappealing outer surface covering the filter assemblies 1300, which is inkeeping with the overall appearance of the fan assembly 1000. The arrayof apertures that define the air inlet 1405 of the shroud 1400 are sizedto prevent larger particles from passing through to the filter assembly1300 and blocking, or otherwise damaging, the filter media 1321-1324.

In order to releasably attach each perforated shroud 1400 to arespective filter frame 1310, the perforated shroud is provided with afirst end flange 1411 that extends radially/perpendicularly away fromthe first curved end 1401 of the perforated shroud 1400 and a second endflange 1412 that extends radially/perpendicularly away from theopposite, second curved end 1402 of the perforated shroud 1400. Thefirst end flange 1411 and second end flange 1412 of the perforatedshroud 1400 are arranged to slide over the end flanges 1311, 1312 of thefilter frame 1310 so that the perforated shroud 1400 is supported on thefilter frame 1310. The first end flange 1411 and second end flange 1412of the perforated shroud 1400 are then each formed with a through-hole1420 a, 1420 b that is arranged to be releasably engaged by acorresponding shroud retention member 1340 a, 1340 b provided on the endflanges of the filter frame 1310.

As illustrated in FIG. 5b , a first shroud retention member 1340 a isprovided on the first end flange 1311 of the filter frame 1310 and asecond shroud retention member 1340 b provided on the opposing, secondend flange 1312 of the filter frame 1310. The first shroud retentionmember 1340 a and the second shroud retention member 1340 b eachcomprise a resilient catch or hook that is arranged to engage acorresponding through-hole 1420 a, 1420 b provided on the shroud 1400.The resilient catch or hook provided on each end flange 1311, 1312 ofthe filter frame 1310 comprises a resilient arm/tab 1341 that extends ina direction that is parallel to a plane that bisects the filter frame1310. A distal end of the resilient arm/tab 1341 is then provided with asloped projection 1342 that projects/extends away from theexterior/external surface of the flange 1311, 1312 and slopes downwardstowards the distal end of the resilient arm/tab 1341.

When the shroud 1400 is slid onto the filter frame 1310, the slopedprojection 1342 contacts an end flange 1311, 1312 of the shroud 1400thereby forcing the resilient arm/tab 1341 to bend/flex downwards. Thesloped projection 1342 then enters the through-hole 1420 a, 1420 bprovided on the end flange 1411, 1412 of the shroud 1400 when the shroud1400 is far enough over the filter frame 1310 such that the resilientarm/tab 1341 is then free to return to its original unbentconfiguration, with the sloped projection 1342 extending through thethrough-hole 1420 a, 1420 b. When a user wishes to separate the shroud1400 from the filter frame 1310, they apply a downward force onto eachsloped projection 1342 and simultaneously begin to slide the shroud 1400away from the filter frame 1310. The downward force causes the resilientarm/tab 1341 to bend/flex downwards and out of engagement with thethrough-hole 1420 a, 1420 b such that the shroud 1400 is then free toslide off the filter frame 1310.

In order to assist with the mounting of the shroud 1400 onto the filterframe 1310, both the first end flange 1311 and second end flange 1312 ofthe filter frame 1310 are formed with alignment ribs 1351, 1352 that areeach arranged to cooperate with a corresponding track or channel orgroove 1431, 1432 provided on the shroud 1400 in order to guide theshroud 1400 onto the filter frame 1300 such that each of the shroudretention members 1340 engages a respective shroud retention though-hole1420 a, 1420 b. Each alignment rib 1351, 1352 is straight and extends ina direction that is parallel to a longitudinal plane that bisects thefilter frame 1310 (i.e. parallel to the direction in which the shroud1400 will be slid on and off the filter frame 1310) and is thereforeperpendicular to the longitudinal axis of the filter frame 1310.

In the illustrated embodiment, both the first end flange 1311 and secondend flange 1312 of the filter frame 1310 are formed with a first pair ofalignment ribs 1351 that project/extend away from and extend along theexterior/external surface of the flange 1311, 1312, with a first of thepair of alignment ribs 1351 being provided adjacent to the first side ofthe flange and a second of the pair of alignment ribs 1351 beingprovided adjacent to the second side of the flange. The shroud 1400 isthen formed with a pair of corresponding grooves or channels 1431, witheach of the pair of grooves or channels corresponding to one of thefirst pair of alignment ribs 1351. These grooves or channels 1431 taperoutwardly from an inner end 1431 a to a mouth 1431 b through which oneof first pair of the alignment ribs 1351 can enter (i.e. slide into) thegroove/channel 1431. The mouth 1431 b is therefore larger than the innerend 1431 a of the channel 1431, thereby making it easier to align eachrib 1351 with the mouth 1431 b of the corresponding channel/groove 1431,with the tapering of the groove/channel 1431 then guiding the rib 1351towards the inner end 1431 a and a position in which the shroud 1400 isaligned so that the through-holes 1420 a, 1420 b will be engaged by theshroud retention member 1340 provided on the corresponding flange 1311,1312 of the filter frame 1310.

Both the first end flange 1311 and second end flange 1312 of the filterframe 1310 are also formed with a second pair of alignment ribs 1352that project/extend away from and extend along the exterior/externalsurface of the flange 1311, 1312, with each of the second pair ofalignment ribs 1352 being provided on opposite sides of the shroudretention member 1340 provided on the flange 1311, 1312. The shroud 1400is then formed with one further groove or channel 1432 that extends intothe inner surface of the shroud flange 1411, 1412 around thethrough-hole 1420. This further groove or channel 1432 also tapersoutwardly from an inner end 1432 a to a mouth 1432 b through which bothof the second pair of alignment ribs 1352 can enter (i.e. slide into)the groove/channel 1432. The mouth 1432 b is therefore larger than theinner end 1432 a of the channel 1432 thereby making it easier to alignthe second pair of alignment ribs 1352 with the mouth 1432 b of thefurther channel/groove 1432, with the tapering of the furthergroove/channel 1432 then guiding the second pair of alignment ribs 1352towards the inner end 1432 a and the position in which the shroud 1400is aligned so that the through-holes 1420 a, 1420 b will be engaged bythe shroud retention member 1340 provided on the corresponding flange1311, 1312 of the filter frame 1310.

As shown in FIG. 5b , each filter frame 1310 is provided with twoengagement members 1371 a, 1371 b. A first engagement member 1371 a isprovided on the first edge 1313 of the filter frame 1310 and a secondengagement member 1371 b on the opposing, second edge 1314 of the filterframe 1310, the first engagement member 1371 a being configured to beengaged by the first retention assembly 1500 a and the second engagementmember 1371 b being configured to be engaged by the second retentionassembly 1500 b. Specifically, the first edge 1313 of the filter frame1310 is that provided on a first of the straight sides of the filterframe 1310 whilst the second edge 1314 of the filter frame 1310 is thatprovided on a second of the straight sides of the filter frame 1310,with these two straight sides being parallel to the longitudinal axis ofthe filter frame 1310. The first engagement member 1371 a and the secondengagement member 1371 b therefore project perpendicularly away from thestraight sides of the filter frame 1310.

In the illustrated embodiment, the first engagement member 1371 aprovided on the first edge 1313 of the filter frame 1310 is locatedtowards a first end 1311 of the filter frame 1310, and the secondengagement member 1371 b provided on the second edge 1314 of the filterframe 1310 is located towards an opposing, second end 1312 of the filterframe 1310. The distance between the first engagement member 1371 a andthe first end 1311 of the filter frame 1310 is equal to the distancebetween the second engagement member 1371 b and the second end 1312 ofthe filter frame 1310. The first engagement member 1371 a is thereforeadjacent to a first corner of the filter frame 1310 and the secondengagement member 1371 b is adjacent to a diagonally opposing secondcorner of the filter frame 1310. Specifically, as the filter frame 1310substantially has the shape of a semi-cylinder, the first engagementmember 1371 a of the filter frame 1310 is located on a first straightedge of the filter frame 1310 towards the top curved end of the filterframe 1310, whilst the second engagement member 1371 b of the filterframe 1310 is located on a second straight edge of the filter frame 1310towards the bottom curved end of the filter frame 1310.

The first engagement member 1371 a and the second engagement member 1371b are each configured to be engaged by a retention assembly 1500 of thefan assembly 1000 when the filter frame 1310 is mounted on the fanassembly 1000. In the illustrated embodiment, the first and secondengagement members 1371 a, 1371 b each comprise a pair of hooks thatface in opposing directions. Each hook comprises a projection 1372extending from the filter frame that has a distal end 1373 that isangled relative to a proximal end, with the distal end 1373 extending ina direction that is parallel to the longitudinal axis of the filterframe 1310. In particular, each pair of hooks comprises a singleprojection 1372 extending from the filter frame 1310 that has a distalend 1373 comprising a pair of angled portions that are parallel to thelongitudinal axis of the filter frame 1310 and that extend in opposingdirections. In other words, the first and second engagement members 1371a, 1371 b each comprise a generally T-shaped projection that extendsfrom a horizontal edge of the filter frame 1310, with the pair of hooksbeing provided by the distal end of the T-shaped projection. The firstand second engagement members 1371 a, 1371 b therefore each havetwo-fold rotational symmetry.

The filter frame 1310 as a whole therefore has two-fold rotationalsymmetry such that the filter frame 1310 can be mounted on the fanassembly 1000 irrespective of which of the curved ends of the filterframe 1310 is located at the top (i.e. in either of two opposingorientations). Furthermore, the two filter frames 1310 a, 1310 b mountedon the fan assembly 1000 are identical and are thereforeinterchangeable.

In order to retain the filter assemblies 1300 a, 1300 b on the main bodysection 1110, the fan assembly 1000 comprises a pair of retentionassemblies 1500 a, 1500 b that cooperate to releasably retain the twofilter assemblies 1300 a, 1300 b on the fan body 1100. To do so, eachretention assembly 1500 is configured to engage with one or more of theengagement members 1371 provided on the filter frame 1310 when thefilter frame 1310 is mounted on the fan assembly 1000. Each retentionassembly 1500 then further comprises a release mechanism 1560 that isarranged to cause the retention assembly 1500 to release the filterassembly 1300 when operated by a user.

In the illustrated embodiment, the fan assembly 1000 comprises tworetention assemblies 1500 a, 1500 b that each mounted/attached to theouter surface of the main body section 1110 so that they extendlongitudinally along the outer surface of the main body section 1110,with the retention assemblies 1500 a, 1500 b being diametrically opposedto one another. In other words, the two retention assemblies 1500 a,1500 b are located opposite one another on the main body section 1110such that a plane passing through a longitudinal axis of the firstretention assembly 1500 a and a longitudinal axis of the secondretention assembly 1500 b bisects the main body section 1110. Theretention assemblies 1500 a, 1500 b are therefore separated by 180degrees. The outer surface of the main body section 1110 is thereforedivided into two separate halves by the two separate retentionassemblies 1500 a, 1500 b. The first air inlet 1130 a and the second airinlet 1130 b therefore extend around a periphery of the fan body 1100,except for the locations of the retention assemblies 1500 a, 1500 b, andrespectively cover the entirety of the area between the first retentionassembly 1500 a and the second filter assembly 1500 b.

The first retention assembly 1500 a is configured to releasably engagethe first filter frame 1310 a adjacent to a first straight edge of thefirst filter frame 1310 a and the second retention assembly 1500 b isconfigured to releasably engage the first filter frame 1310 a adjacentto an opposing, second straight edge of the first filter frame 1310 a.In order to minimise the surface area consumed by the retentionassemblies, the first retention assembly 1500 a is configured to alsoreleasably engage the second filter frame 1310 b adjacent to a firststraight edge of the second filter frame 1310 b and the second retentionassembly 1500 b is configured to also releasably engage the secondfilter frame 1310 b adjacent to an opposing, second straight edge of thesecond filter frame 1310 b. The two retention assemblies 1500 a, 1500 btherefore cooperate to retain both the first filter frame 1310 a and thesecond filter frame 1310 b on the main body section 1110 by eachengaging opposite edges of the two filter frames 1310 a, 1310 b. Therelease mechanisms 1560 of each of the first retention assembly 1500 aand the second retention assembly 1500 b are therefore arranged to causethe respective retention assembly 1500 to simultaneously release the twofilter frames 1310 a, 1310 b when operated by a user.

FIG. 7a shows a front exploded view of a retention assembly 1500 andFIG. 7b shows a rear exploded view of a retention assembly 1500. In theembodiment illustrated in FIGS. 7a and 6b , each of the retentionassemblies 1500 comprises a housing 1510 that is formed from a firsthousing section 1511 and a second housing section 1512 that areconnected together. The first housing section 1511 is provided with twocatch openings 1513, 1514 one in each of the opposing longitudinal sidesof the first housing section 1511 and with each being located towardsopposite ends of the housing 1510. The distance between the firstopening 1513 and a first end of the housing 1500 is equal to thedistance between the second opening 1514 and a second end of the housing1500.

The retention assemblies 1500 each further comprise two bistable catches1520 mounted within the housing 1510 and that are each aligned with acorresponding one of the catch openings 1513, 1514. The two bistablecatches 1520 a, 1520 b are therefore disposed one above the other withinthe housing 1510 such that they are at different locations along thelongitudinal axis of the housing 1510 of the retention assembly 1500(i.e. towards opposite ends of the housing 1510) and face in opposingdirections. As illustrated in FIG. 4, the housings 1510 of each of theretention assemblies 1500 are then mounted longitudinally along theouter surface of the main body section 1110. The upper bistable catch1520 a can therefore engage with the first engagement member 1371 aprovided on a first edge of a first of the two filter assembles 1300 a,whilst the lower bistable catch 1520 b can engage with the firstengagement member 1371 a provided on a first edge of a second of the twofilter assembles 1300 b.

The two bistable catches 1520 a, 1520 b of the retention assembly 1500are each arranged, in a first stable state, to engage an engagementmember 1371 provided on a filter frame 1310 and thereby retain thefilter assembly 1300 on the fan body 1100. Each bistable catch 1520 a,1520 b is also arranged, in a second stable state, to disengage theengagement member 1371 provided on the filter frame 1310 and therebyrelease the filter assembly 1300 from the main body section 1110.

FIG. 7c shows a perspective view of the retention assembly 1500 of FIGS.7a and 7b together with enlarged views of the bistable catches 1520 a,1520 b. In the illustrated embodiment, each bistable catch 1520 a, 1520b comprises a catch body 1540 rotatably mounted within the housing 1510of the retention assembly 1500 adjacent to a corresponding catch opening1513, 1514 and a resilient member 1550 in the form of a torsion springconnected between the catch body 1540 and the housing 1510, the torsionspring 1550 being arranged to provide an over-centre action thatswitches the catch body 1540 between the first stable state and thesecond stable state.

The catch body 1540 comprises a first cam surface 1541 that is arrangedto cause rotation of the catch body 1540 from the second stable state tothe first stable state when an engagement member 1371 provided on afilter frame 1310 is inserted into the housing 1510 of the retentionassembly 1500 through the corresponding opening 1513, 1514. The catchbody 1540 further comprises a retention surface 1542 that is arranged toretain the engagement member 1371 provided on the filter frame 1310within the housing 1510 of the retention assembly 1500 when the catchbody 1540 is in the first stable state. The catch body 1540 then furthercomprises a second cam surface 1543 that is arranged to cause rotationof the catch body 1540 from the first stable state to the second stablestate when the release mechanism 1560 is operated by a user.

The release mechanism 1560 of each retention assembly 1500 thencomprises a button 1561 that is arranged to cause movement of a releasemember 1562 when operated by a user, the release member 1562 beingarranged such that movement of the release member 1562 causes both ofthe bistable catches 1520 a, 1520 b to switch from the first stablestate. To do so, the release member 1562 is arranged to be held by aresilient member 1563, in the form of a return or compression spring, inan initial/end position in which the release member 1562 allows both ofthe bistable catches 1520 a, 1520 b to remain in the first stable state.Movement of the release member 1652 by a user is then against aresistance provided by the return/compression spring 1563, with thereturn/compression spring 1563 causing the release member 1562 to returnto the initial/end position when the force applied to the release member1562 by the user is removed.

As illustrated in FIGS. 7a, 7b and 7c , the button 1561 is provided onthe release member 1562, the release member 1562 being located withinthe housing 1510 with the button 1561 being aligned with and projectingthrough a button opening 1515 formed in the first housing section 1511so that the button 1561 is accessible to the user. The release member1562 is then arranged to slide within the housing 1510 of the retentionassembly 1500 when the button 1561 is pressed by a user. To do so, thebutton 1561 is arranged so that when the user presses on the button 1561in a direction that is parallel to the longitudinal axis of the housing1510, the button 1561 moves longitudinally within the button opening1515. Being provided on the release member 1562, the longitudinalmovement of the button 1561 causes corresponding longitudinal movementof the release member 1562 within the housing 1510 against theresistance provided by the compression spring 1563, with the compressionspring 1563 being connected between the release member 1562 and thehousing 1510.

The release member 1562 is then provided with two projections/tabs 1564,1565 that are arranged to push against the second cam surface 1543 ofeach catch body 1540 as the release member 1562 slides away from itsinitial/end position and thereby cause rotation of the catch body 1540from the first stable state to the second stable state. Theprojections/tabs 1564, 1565 provided on the release member 1562 arearranged such that both the upper bistable catch 1520 a and the lowerbistable catch 1520 b of the retention assembly 1500 simultaneouslyswitch from the first stable state. The longitudinal movement of therelease member 1562 within the housing 1510 against the resistanceprovided by the compression spring 1563 therefore results in the releaseof the two engagement members 1371 retained by the retention assembly1500.

As two retention assemblies 1500 a, 1500 b cooperate to retain both thefirst filter frame 1310 a and the second filter frame 1310 b on the mainbody section 1110, the complete release of the first filter frame 1310 aand the second filter frame 1310 b from the main body section 1110requires the operation of the release mechanisms 1560 a, 1560 b of bothretention assemblies 1500 a, 1500 b. Whilst this can be performedconsecutively, with the release mechanism 1560 of one of the retentionassemblies 1500 a, 1500 b being operated before the other, the releasebutton 1561 of each release mechanism 1560 a, 1560 b can be operatedusing a single digit such that a user could operate both releasemechanisms concurrently; using one hand for each release mechanism 1560a, 1560 b.

To further illustrate the functioning of the retention assembly 1500,FIG. 8 shows a cutaway view of one of the retention assemblies 1500 inwhich an engagement member 1371 provided on a filter frame 1310 isengaged by the lower bistable catch 1520 b of the retention assembly1500. As can be seen in FIG. 8, the upper bistable catch 1520 a of theretention assembly 1500 is in the second stable state with the first camsurface 1541 of the upper bistable catch 1520 a facing the upper catchopening 1513 of the housing 1510. The insertion of an engagement member1371 into the housing 1510 through the upper catch opening 1513 wouldtherefore cause rotation of the catch body 1540 from the second stablestate to the first stable state. The upper bistable catch 1520 a cantherefore be considered to be open.

In contrast, the lower bistable catch 1520 b of the retention assembly1500 is in the first stable state with the retention surface 1542 of thelower bistable catch 1520 b engaged with the one of the projecting hooksof the engagement member 1371 that has been inserted through the lowercatch opening 1514 of the housing 1510. The lower bistable catch 1520 bcan therefore be considered to be closed. In addition, in the firststable state the second cam surface 1543 of the lower bistable catch1520 b is facing the lower tab 1565 that projects from the releasemember 1562. The sliding movement of the release member 1562 against theresistance provided by the compression spring 1563 would therefore causethe lower tab 1565 to push against the second cam surface 1543 of thecatch body 1540, which would in-turn cause rotation of the catch body1540 from the first stable state to the second stable state, therebyreleasing the engagement member 1371 currently engaged by the catch body1540. In addition, rotation of the catch body 1540 from the first stablestate to the second stable state would also cause the first cam surface1541 to push against the engagement member 1371 so as to drive it out ofthe housing 1500 through the adjacent opening 1514.

The fan assemblies described herein are therefore provided with filterassemblies that can easily be removed by a user, so that the filtermedia can be replaced if required, without the need to remove the nozzleand without the need for tools. In addition, whilst the fan assembliesdescribed herein individually only cover a portion of the body of thefan assembly so that they are easier to remove, the mechanisms forretaining and releasing the filter assemblies are optimised so as toonly cover a minimal portion of the fan body thereby maximising the areaavailable for the air inlets and corresponding filter media.Furthermore, the mechanisms for retaining and releasing the filterassemblies automatically retain the filter assemblies when they aremounted on the fan body, whilst allowing the user to simultaneouslyrelease multiple filter assemblies by operating a release button using asingle digit. Moreover, the identical filter assemblies and themechanisms for retaining and releasing the filter assemblies all havetwo-fold rotational symmetry so that the filter assemblies can beretained on the fan body in either of two opposing orientations, furthersimplifying there removal and replacement by a user.

It will be appreciated that individual items described above may be usedon their own or in combination with other items shown in the drawings ordescribed in the description and that items mentioned in the samepassage as each other or the same drawing as each other need not be usedin combination with each other. In addition, the expression “means” maybe replaced by actuator or system or device as may be desirable. Inaddition, any reference to “comprising” or “consisting” is not intendedto be limiting in any way whatsoever and the reader should interpret thedescription and claims accordingly.

Furthermore, although the invention has been described in terms ofpreferred embodiments as set forth above, it should be understood thatthese embodiments are illustrative only. Those skilled in the art willbe able to make modifications and alternatives in view of the disclosurewhich are contemplated as falling within the scope of the appendedclaims. For example, those skilled in the art will appreciate that theabove-described invention might be equally applicable to other types ofenvironmental control fan assemblies, and not just free standing fanassemblies. By way of example, such a fan assembly could be any of afreestanding fan assembly, a ceiling or wall mounted fan assembly and anin-vehicle fan assembly.

By way of further example, whilst the above described embodiments allrelate to fan assemblies having a circular cylindrical fan body, variousfeatures described above would be equally applicable to embodiments inwhich the fan body has a shape other than cylindrical. For example, thefan body could have the shape of an elliptic cylinder, a cube or anyother prism.

In addition, whilst the filter assemblies of the above describedembodiments comprise only a single pair of engagement members, each ofwhich are provided on opposing straight edges of the filter frame, thoseskilled in the art will appreciate that larger filter assemblies mayrequire multiple pairs of engagement members, with the engagementmembers of each pair being on opposing straight edges of the filterframe. Such larger filter assemblies may therefore comprise multipleengagement members that are distributed along each of the opposingstraight edges of the filter frame, whilst preferably maintaining thetwo-fold rotational symmetry of the filter frame. In this case, whilstit is preferable that the fan assembly has only a single pair ofretention assemblies that cooperate to releasably retain both filterassemblies on the fan body, particularly larger filter assemblies mayrequire two separate pairs of retention assemblies, with a first paircooperating to releasably retain a first of the two filter assemblies onthe fan body and a second pair cooperating to releasably retain a secondof the two filter assemblies on the fan body.

1. A filter assembly arranged to be mounted over the air inlet of a fanassembly, the filter assembly comprising: a filter frame arranged tosupport one or more filter media; wherein the filter frame is providedwith a first engagement member on a first edge of the filter frame and asecond engagement member on a second edge of the filter frame, the firstedge being opposite to the second edge; and wherein the first engagementmember and the second engagement member are each configured to beengaged by a respective retention assembly when mounted on the fanassembly.
 2. The filter assembly of claim 1, wherein the filter framehas two-fold rotational symmetry such that the filter frame can beretained on the fan assembly in either of two opposing orientations. 3.The filter assembly of claim 1, wherein the first engagement memberprovided on the first edge of the filter frame is located towards afirst end of the filter frame, and the second engagement member providedon the second edge of the filter frame is located towards an opposing,second end of the filter frame.
 4. The filter assembly of claim 3,wherein a distance between the first engagement member and the first endof the filter frame is equal to a distance between the second engagementmember and the second end of the filter frame.
 5. The filter assembly ofclaim 1, wherein the first engagement member is adjacent to a firstcorner of the filter frame and the second engagement member is adjacentto a diagonally opposing second corner of the filter frame.
 6. Thefilter assembly of claim 1, wherein the first engagement member and thesecond engagement member each comprise a pair of hooks that face inopposing directions.
 7. The filter assembly of claim 6, wherein eachhook comprises a projection extending from the filter frame having adistal end that is angled relative to a proximal end, the distal endextending in a direction that is parallel to the longitudinal axis ofthe filter frame.
 8. The filter assembly of claim 7, wherein each pairof hooks comprises a single projection extending from the filter framehaving a distal end comprising a pair of angled portions that areparallel to the longitudinal axis of the filter frame and that extend inopposing directions.
 9. The filter assembly of claim 1, wherein thefilter frame is provided with a first side flange that extends along afirst side of the filter frame and a second side flange that extendsalong a second side of the filter frame.
 10. The filter assembly ofclaim 9, wherein the first engagement member is provided on the firstside flange and the second engagement member is provided on the secondside flange.
 11. The filter assembly of claim 1, wherein the filterframe is provided with a first end flange that extends along a first endof the filter frame and a second side flange that extends along a secondend of the filter frame, the first end flange and the second end flangebeing arranged to support the one or more filter media.
 12. The filterassembly of claim 1, wherein the filter frame is provided with a sealthat extends around the entirety of an inner periphery of the filterframe.
 13. The filter assembly of claim 12, wherein the filter frame isprovided with a recess that that extends around the entirety of theinner periphery of the filter frame and that is arranged to received andsupport the seal.
 14. The filter assembly of claim 13, wherein therecess extends across an inner surface of both the first side flange andsecond side flange, and across an inner edge of both the first end andthe second end of the filter frame.
 15. The filter assembly of claim 1,and further comprising: a first retention member provided on a first endof the filter frame and a second retention member provided on anopposing, second end of the filter frame, wherein the first retentionmember and the second rotation member are arranged to releas ably retaina shroud when mounted on the filter assembly.
 16. The filter assembly ofclaim 15, wherein each of the first retention member and the secondretention member comprise a resilient catch or hook that is arranged toengage a corresponding through-hole provided on the shroud.
 17. Thefilter assembly of claim 16, wherein the resilient catch or hookcomprises a resilient arm, a distal end of the resilient arm beingprovided with a sloped projection, wherein the sloped projection slopestowards the distal end of the resilient arm/tab.
 18. The filter assemblyof claim 15, wherein the filter frame is provided with one or morealignment ribs that are arranged to cooperate with a corresponding trackor channel or groove provided on the shroud in order to guide the shroudonto the filter frame.
 19. The filter assembly of claim 18, wherein theone or more alignment ribs is straight and extends in a direction thatis parallel to a longitudinal plane that bisects the filter frame. 20.The filter assembly of claim 18, wherein the filter frame is providedwith at least one alignment rib on each end of the filter frame.
 21. Thefilter assembly of claim 20, wherein the filter frame is provided with afirst end flange that extends along a first end of the filter frame anda second side flange that extends along a second end of the filterframe, the first end flange and the second end flange being arranged tosupport the one or more filter media, and the first end flange and thesecond end flange of the filter frame are each provided with a pair ofalignment ribs.
 22. The filter assembly of claim 21, wherein the firstend flange and the second end flange of the filter frame are eachprovided with a further pair of alignment ribs.
 23. The filter assemblyof claim 1, wherein the filter assembly is semi-cylindrical in shape.24. The filter assembly of claim 1, wherein the edges of the filterframe are parallel to the longitudinal axis of the filter frame and theends of the filter frame are perpendicular to a longitudinal axis of theof the filter frame and have an arc-shaped cross section in a planeperpendicular to longitudinal axis.